diff --git a/base/base_tests/bits_test.cpp b/base/base_tests/bits_test.cpp
index c2a43733ea..5263246dae 100644
--- a/base/base_tests/bits_test.cpp
+++ b/base/base_tests/bits_test.cpp
@@ -120,14 +120,14 @@ UNIT_TEST(PopCount64)
 
 UNIT_TEST(CeilLog)
 {
-  TEST_EQUAL(0, bits::CeilLog(0x0), ());
-  TEST_EQUAL(0, bits::CeilLog(0x1), ());
-  TEST_EQUAL(1, bits::CeilLog(0x2), ());
-  TEST_EQUAL(1, bits::CeilLog(0x3), ());
-  TEST_EQUAL(2, bits::CeilLog(0x4), ());
+  TEST_EQUAL(0, bits::FloorLog(0x0), ());
+  TEST_EQUAL(0, bits::FloorLog(0x1), ());
+  TEST_EQUAL(1, bits::FloorLog(0x2), ());
+  TEST_EQUAL(1, bits::FloorLog(0x3), ());
+  TEST_EQUAL(2, bits::FloorLog(0x4), ());
 
-  TEST_EQUAL(6, bits::CeilLog(0x7f), ());
-  TEST_EQUAL(7, bits::CeilLog(0x80), ());
-  TEST_EQUAL(31, bits::CeilLog(0xFFFFFFFF), ());
-  TEST_EQUAL(63, bits::CeilLog(0xFFFFFFFFFFFFFFFF), ());
+  TEST_EQUAL(6, bits::FloorLog(0x7f), ());
+  TEST_EQUAL(7, bits::FloorLog(0x80), ());
+  TEST_EQUAL(31, bits::FloorLog(0xFFFFFFFF), ());
+  TEST_EQUAL(63, bits::FloorLog(0xFFFFFFFFFFFFFFFF), ());
 }
diff --git a/base/bits.hpp b/base/bits.hpp
index ad0eeac236..fda447185a 100644
--- a/base/bits.hpp
+++ b/base/bits.hpp
@@ -70,7 +70,7 @@ namespace bits
     return static_cast<uint32_t>(x);
   }
 
-  inline uint8_t CeilLog(uint64_t x) noexcept
+  inline uint8_t FloorLog(uint64_t x) noexcept
   {
 #define CHECK_RSH(x, msb, offset) \
     if (x >> offset)              \
diff --git a/base/small_set.hpp b/base/small_set.hpp
index de1dad1406..35c7afe7a1 100644
--- a/base/small_set.hpp
+++ b/base/small_set.hpp
@@ -54,7 +54,7 @@ public:
     {
       ASSERT_NOT_EQUAL(m_current_block, 0, ());
       auto const bit = m_current_block & -m_current_block;
-      return bits::PopCount(bit - 1) + m_current_block_index * 64;
+      return bits::FloorLog(bit) + m_current_block_index * 64;
     }
 
     Iterator const & operator++()
diff --git a/coding/compressed_bit_vector.cpp b/coding/compressed_bit_vector.cpp
index d52eaffb6d..88a863c27f 100644
--- a/coding/compressed_bit_vector.cpp
+++ b/coding/compressed_bit_vector.cpp
@@ -434,7 +434,7 @@ unique_ptr<CompressedBitVector> CompressedBitVectorBuilder::FromBitGroups(
   if (bitGroups.empty())
     return make_unique<SparseCBV>(move(bitGroups));
 
-  uint64_t const maxBit = kBlockSize * (bitGroups.size() - 1) + bits::CeilLog(bitGroups.back());
+  uint64_t const maxBit = kBlockSize * (bitGroups.size() - 1) + bits::FloorLog(bitGroups.back());
   uint64_t popCount = 0;
   for (size_t i = 0; i < bitGroups.size(); ++i)
     popCount += bits::PopCount(bitGroups[i]);
diff --git a/coding/elias_coder.hpp b/coding/elias_coder.hpp
index e7cc92e494..47b183b4b1 100644
--- a/coding/elias_coder.hpp
+++ b/coding/elias_coder.hpp
@@ -18,7 +18,7 @@ public:
     if (value == 0)
       return false;
 
-    uint8_t const n = bits::CeilLog(value);
+    uint8_t const n = bits::FloorLog(value);
     ASSERT_LESS_OR_EQUAL(n, 63, ());
 
     uint64_t const msb = static_cast<uint64_t>(1) << n;
@@ -50,7 +50,7 @@ public:
     if (value == 0)
       return false;
 
-    uint8_t const n = bits::CeilLog(value);
+    uint8_t const n = bits::FloorLog(value);
     ASSERT_LESS_OR_EQUAL(n, 63, ());
     if (!GammaCoder::Encode(writer, n + 1))
       return false;